Salt intake and regulation in two passerine nectar drinkers: white-bellied sunbirds and New Holland honeyeaters

Purchase, Cromwell; Nicolson, Susan W.; Fleming, Patricia A.

doi:10.1007/s00360-012-0722-3

Cited by 5 publications

(4 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In summary, Egyptian fruit bats did not increase food intake rate when salt was added to their diet of dilute solutions was not affected by sugar type. Our sample size was small but our study, along with observations made on Pallas's long-tongued bat (Bakken et al, 2008), indicate that, in contrast to birds (Purchase et al, 2010;Purchase et al, 2013), intake of sugary solutions by plant-eating bats is negatively affected when salt is added. However, we do not reject the possibility that lower [NaCl] than the concentration used in our study might benefit their intake rate of dilute sugar solutions, or that Egyptian fruit bats might respond positively to the addition of other electrolytes.…”

Section: Sugar Type and Food Intakementioning

confidence: 56%

The relationships between food and energy intakes, salt content and sugar types in Egyptian fruit bats

M.¹,

Cruz‐Neto²,

Wojciechowski³

et al. 2015

Mammalian Biology

View full text Add to dashboard Cite

Frugivorous animals may face an osmoregulatory challenge due to the watery nature of their food and low concentration of electrolytes therein. We examined the effects of salt content (NaCl) and sugar type (sucrose vs. glucose) on the intake rate of dilute sugar solutions by the Egyptian fruit bat (Rousettus aegyptiacus). Increased salt content did not bring about an increase in energy intake by bats fed dilute sucrose diets and the bats did not compensate by hyperphagia to achieve the energy intake of bats fed concentrated sucrose solution without salt. Moreover, increasing salt content had a negative effect on the total energy intake of Egyptian fruit bats fed equicaloric sucrose solutions. There were no differences in hematocrit in bats fed the diets of different sucrose concentration, but plasma osmolality was higher in those bats fed more concentrated sugar solutions, and urine osmolality was higher in those fed on highsalt diets. Food and energy intake did not differ between bats that were fed dilute glucose and sucrose solutions. Our findings indicate that Egyptian fruit bats do not modulate food intake when salt content of dilute sugar solutions is increased, and that increasing salt content might constrain their food intake rate. Sugar type did not affect food intake by Egyptian fruit bats, indicating that sucrose hydrolysis alone does not limit the intake of dilute sugar nectar.

show abstract

Section: Sugar Type and Food Intakementioning

confidence: 56%

The relationships between food and energy intakes, salt content and sugar types in Egyptian fruit bats

M.¹,

Cruz‐Neto²,

Wojciechowski³

et al. 2015

Mammalian Biology

View full text Add to dashboard Cite

show abstract

“…Sunbirds reduced CF output to 0.004 ml/h on a concentrated 2.5 M sucrose diet compared to 1.4 ml/h on a dilute 0.25 M sucrose diet (Fleming et al 2004a). High CF osmolalities ( ̴ 450 mOsm/kg) were recorded when birds were presented with either 2.5 M sucrose or 0.63 M sucrose containing 200 mM NaCl (Fleming and Nicolson 2003;Purchase et al 2013b). White-bellied sunbirds are able to modulate their glomerular filtration rate, effectively shutting down urine production to avoid potential dehydration during the overnight fast period (Fleming et al 2004b;Purchase et al 2013a).…”

Section: Discussionmentioning

confidence: 99%

Detoxification and elimination of nicotine by nectar-feeding birds

2017

View full text Add to dashboard Cite

Many dilute nectars consumed by bird pollinators contain secondary metabolites, potentially toxic chemicals produced by plants as defences against herbivores. Consequently, nectar-feeding birds are challenged not only by frequent water excess, but also by the toxin content of their diet. High water turnover, however, could be advantageous to nectar consumers by enabling them to excrete secondary metabolites or their transformation products more easily. We investigated how the alkaloid nicotine, naturally present in nectar of Nicotiana species, influences osmoregulation in white-bellied sunbirds Cinnyris talatala and Cape white-eyes Zosterops virens. We also examined the metabolic fate of nicotine in these two species to shed more light on the post-ingestive mechanisms that allow nectar-feeding birds to tolerate nectar nicotine. A high concentration of nicotine (50 µM) decreased cloacal fluid output and increased its osmolality in both species, due to reduced food intake that led to dehydration. White-eyes excreted a higher proportion of the ingested nicotine-containing diet than sunbirds. However, sugar concentration did not affect nicotine detoxification and elimination. Both species metabolised nicotine, excreting very little unchanged nicotine. Cape white-eyes mainly metabolised nicotine through the cotinine metabolic pathway, with norcotinine being the most abundant metabolite in the excreta, while white-bellied sunbirds excreted mainly nornicotine. Both species also utilized phase II conjugation reactions to detoxify nicotine, with Cape white-eyes depending more on the mercapturic acid pathway to detoxify nicotine than white-bellied sunbirds. We found that sunbirds and white-eyes, despite having a similar nicotine tolerance, responded differently and used different nicotine-derived metabolites to excrete nicotine.

show abstract

“…Importantly, sunbird [e.g. up to 500±40 mOsmol kg -1 (Purchase et al, 2013a)] and honeyeater [370±30 mOsmol kg -1 (Purchase et al, 2013a)] species can produce urine that is markedly hyperosmotic compared with plasma, surpassing the ability of rufous hummingbirds, Selasphorus rufus, which become salt loaded when feeding on 0.63 mol l −1 sucrose diets with even moderate quantities (35 mmol l −1 ) of sodium chloride added (Lotz and Martínez del Rio, 2004). Hummingbirds are therefore specialized for dealing with water loading and retrieval of electrolytes, while honeyeaters and sunbirds are additionally capable of dealing with dehydration and electrolyte loading.…”

Section: Commentarymentioning

confidence: 99%

“…Post-renal modification is important in osmoregulation of birds, and recovery of Na + and K + ions has been demonstrated in hummingbirds, honeyeaters and sunbirds by comparing their concentrations in ureteral urine and cloacal fluid (Lotz and Martínez del Rio, 2004;Purchase et al, 2013a). However, caution is needed in assessing the contribution of the lower intestine to recovery of electrolytes in birds that modulate intestinal water absorption, because the elimination of non-absorbed water will also dilute the urine.…”

Section: The Potential Role Of Evaporationmentioning

confidence: 99%

Drinking problems on a ‘simple’ diet: physiological convergence in nectar-feeding birds

Nicolson

Fleming

2014

Journal of Experimental Biology

Self Cite

View full text Add to dashboard Cite

Regulation of energy and water are by necessity closely linked in avian nectarivores, because the easily available sugars in nectar are accompanied by an excess of water but few electrolytes. In general, there is convergence in morphology and physiology between three main lineages of avian nectarivores that have evolved on different continents -the hummingbirds, sunbirds and honeyeaters. These birds show similar dependence of sugar preferences on nectar concentration, high intestinal sucrase activity and rapid absorption of hexoses via mediated and paracellular routes. There are differences, however, in how these lineages deal with energy challenges, as well as processing the large volumes of preformed water ingested in nectar. While hummingbirds rely on varying renal water reabsorption, the passerine nectarivores modulate intestinal water absorption during water loading, thus reducing the impact on the kidneys. Hummingbirds do not generally cope with salt loading, and have renal morphology consistent with their ability to produce copious dilute urine; by contrast, as well as being able to deal with dilute diets, honeyeaters and sunbirds are more than capable of dealing with moderately high levels of added electrolytes. And finally, in response to energy challenge, hummingbirds readily resort to torpor, while the passerines show renal and digestive responses that allow them to deal with short-term fasts and rapidly restore energy balance without using torpor. In conclusion, sunbirds and honeyeaters demonstrate a degree of physiological plasticity in dealing with digestive and renal challenges of their nectar diet, while hummingbirds appear to be more constrained by this diet.

show abstract

Salt intake and regulation in two passerine nectar drinkers: white-bellied sunbirds and New Holland honeyeaters

Cited by 5 publications

References 33 publications

The relationships between food and energy intakes, salt content and sugar types in Egyptian fruit bats

The relationships between food and energy intakes, salt content and sugar types in Egyptian fruit bats

Detoxification and elimination of nicotine by nectar-feeding birds

Drinking problems on a ‘simple’ diet: physiological convergence in nectar-feeding birds

Contact Info

Product

Resources

About